1. Field of the Invention
The present invention relates of a communication system with a plurality of participating devices, which communicate with each other by a data line, wherein the data line has one or more connection devices for connecting an interface device for definite communication with a given participating device. Particularly the invention relates to a network with a plurality of participating devices connected in the network and respective defined associated connection devices connected with the network for connecting one or more portable operation and visualization terminals. Further the invention relates to a connection device and an interface device for use in this type of communication system and also to a method of identification of a participating device in this communication system.
2. Description of the Related Art
Current communication systems are used in many technical applications, in which the communication system includes a plurality of participating devices, which are connected with each other by a communication line, in order to be able to communicate with each other by means of the communication line. For example, the control devices used for controlling machines or robots in automated manufacturing plants communicate with each other, in order to guarantee timely synchronized machine operations or robotic motions. The control devices are typically industrial processor systems, for example control means or controllers with a programmable memory or “embedded processor” systems, which do not have their own associated terminal for operating, programming or monitoring, but usually are programmed by a central computer. The central computer is usually connected via data lines with the control devices, so that the central computer is built usually at a remote distant from the manufacturing plant. If an error now occurs in the manufacturing plant operation, it is at least partially unavoidable for an operator to try to find the location of the error or fault, i.e. a simultaneous control both of the program running in the concerned control means and of observation of the machine operations or robotic motions. For this purpose it is thus necessary for the operator to connect a mobile terminal at the location or site with the concerned control means. Usually a connection device either in the connecting line to the central computer or directly to the control means is provided in prior art control systems. Identification information for selection and identification of the concerned and responding control means must usually be given by a terminal, at least in the case, in which the connection device is arranged in the connecting line to the central computer and is not exclusively directly hardwired to the control means. For this purpose the identification information is usually provided in a reference list printed on paper, to which the operator must refer before initiating the communication connection. However it is usually required to continuously adjust and update the reference list to include all changes in the communication system. Especially with frequent changes in the plant this requires a very great deal of work. Furthermore in practice the reference list frequently has errors, whereby erroneous operation or primarily no connection is established.
In order to obtain an improvement German Patent DE 101 10 776 A1 discloses a mobile electronic operating and/or monitoring device, which permits a wireless communication with the control means of a machine to be monitored. A definite association or connection of this operating and/or monitoring device to the control means of the machine to be monitored is possible either by means of an interface for direct wireless location or by means of tuned transmitting and/or reception devices with spatially limited receiving and/or transmitting operating ranges. The operation and/or monitoring of the machine can occur according to this reference, but also by means of other devices besides this prior art device. The disadvantage of the operating and/or monitoring device according to this DE reference is that the wireless transmission devices are very expensive, since both transmitting and receiving devices must be provided. Furthermore a bidirectional protocol, a so-called bidirectional handshake, must take place in order to guarantee mutual identification and mutual transmission and reception readiness. Furthermore it is not possible to provide fixed wired safety circuits, which can be connected with the mobile terminal.